- Disease resistance breeding is the practice of selecting and mating animals based on their inherited ability to resist infections and other diseases. It is an important part of animal breeding, genetic improvement, and sustainable livestock production because healthier animals can experience lower disease-related losses, improved productivity, and better welfare. Genetic disease resistance differs from disease tolerance: resistance reduces the likelihood of infection or limits pathogen multiplication, whereas tolerance enables an animal to maintain health or productivity despite infection.
- Disease resistance is influenced by genetic variation, environmental conditions, pathogen characteristics, nutrition, management, and exposure to infectious agents. Many resistance traits are polygenic, meaning that they are influenced by numerous genes, each contributing a relatively small effect. Other traits may be strongly influenced by specific genes or genetic variants. Genes involved in immune response genetics, pathogen recognition, inflammation, and antibody production can contribute to differences in resistance among animals and breeds.
- The effectiveness of disease resistance breeding depends on identifying reliable selection criteria. These may include disease incidence, infection severity, mortality, clinical symptoms, pathogen load, immune measurements, and records of veterinary treatment. Because disease exposure varies between animals and farms, breeders must distinguish inherited resistance from differences caused by management or environment. Accurate health records, standardized disease definitions, and appropriate statistical models help estimate the breeding values of individual animals.
- Heritability indicates how much of the observed variation in a disease-related trait is attributable to genetic differences within a particular population and environment. When a trait has sufficient heritable variation and can be measured reliably, selection may produce genetic improvement over generations. However, low heritability does not necessarily mean that breeding is ineffective; large datasets, genomic information, and improved recording methods may still support progress.
- Genomic selection can improve disease resistance breeding by using DNA markers across the genome to estimate the genetic merit of animals, including young animals that have not yet experienced disease. Genetic testing may also identify specific disease-associated variants, although a test for one variant cannot predict every aspect of resistance to complex diseases. Genomic prediction accuracy depends on the quality and size of the reference population, the relevance of the recorded traits, and validation in the population where selection will be applied.
- Breeding for disease resistance must consider genetic correlations with production, fertility, growth, behaviour, and other health traits. Selection for a single disease trait may have undesirable consequences if it is genetically associated with reduced performance in other areas. A selection index can combine disease resistance with productivity, reproduction, longevity, welfare, and economic objectives to support balanced genetic improvement.
- Maintaining genetic diversity is also essential. Excessive reliance on a small number of highly selected breeding animals can increase inbreeding and reduce the genetic options available for future disease challenges. Breeders can manage these risks through careful mate selection, monitoring of genetic relationships, and the use of diverse, well-evaluated breeding lines.
- Disease resistance breeding does not replace vaccination, veterinary care, biosecurity, hygiene, adequate nutrition, or sound farm management. Instead, it complements these measures by gradually increasing the inherited capacity of animal populations to cope with specific diseases. When supported by reliable data, balanced selection objectives, and long-term monitoring, disease resistance breeding can contribute to healthier animals, improved production efficiency, and more sustainable livestock systems.
